RFID is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags, tags or transponders. An RFID tag is typically a small object that can be attached to or incorporated into an object, animal, or person. RFID tags may contain silicon chips and antennas to enable them to receive and respond to radio-frequency queries from an RFID transceiver. Passive tags require no internal power source, whereas active tags require a power source.
Active tags can periodically transmit their identification (ID) code, status, data and other information for as long as 10 years on a single battery. Active tags are capable of communicating with devices, such as a reader, at ranges of several hundred feet. Readers are capable of nearly simultaneous detection and reading of hundreds or thousands of tags.
In many RFID systems today, there is a need for localization, i.e., the ability to accurately determine the location of tagged objects, persons or animals to be within a region of desired dimensions. In a hospital setting, for example, it may be useful to know that a particular item of medical equipment or a particular person is somewhere within a relatively large area, e.g., 300 feet in any direction from a receiver or a reader. However, it may be useful to know more precisely where a particular asset, patient or employee is located, and perhaps whether the asset, patient or employee is safe and secure. This may be found from the determined location of the asset, patient or employee; the sensor inputs on the related tag or badge; and/or from a local signpost, that might indicate, for example, that a door is not secure, or smoke has been detected.
Similarly, in a mail or package processing center, for example, it may be useful to know where a specific container is located within a facility, particularly its precise location with respect to key access points, such as the front of a conveyor belt portal or a door. In this way, the system can more effectively route mail or packages in a container to the correct destination. In addition, with improved localization of tracked items down to a particular access point, such as a door, a tag may be turned off (to conserve power) before the related container is loaded on its transport and then turned on upon arrival at a specified destination access point.
Some RFID systems employ radio frequency (RF) signals. Radio frequency signals readily pass through walls, ceilings, floors, etc., however, RF signals also reflect and refract from various objects in the radio transmission path. Therefore, attempting to identify tag location based on RF signal strength has been generally ineffective. Usable RFID localization systems based upon RF signal time-of-flight have been developed and deployed, however, these systems are complex, expensive, and often of limited performance, particularly indoors, because of reflections and other problems.
Other RFID systems employ IR signals, particularly in an IR signpost, and generally provide relatively better and more precise localization. However, existing RFID systems employing IR signals have limited localization capabilities. There is also a need in existing RFID systems employing IR signals to provide system status and other information that, in turn, can greatly enhance asset utilization, productivity and security. There is also a need in existing RFID systems employing IR signals to provide for global interconnection and control of RFID systems where overall control and processing capability may be provided remotely, such as via an Internet website. Moreover, existing RFID systems employing IR signals generally have rigid hardware designs that cannot be adapted for use on multiple applications under programmable processor and system control.
Thus, a need exists for RFID systems employing IR signals that overcome these and other problems.